Angle-resolved Auger spectra of the C2H2 molecule

Auger decay spectra of the ethyne (acetylene) molecule have been measured at photon energies below as well as above the C 1s ionization threshold. Angular anisotropy has been observed at the pi* resonance and in the region of a continuum feature previously assigned to a sigma* resonance, but disappears far above threshold. Because of strong configuration interaction in the final state only high kinetic energy Auger transitions can be assigned to individual electronic states. In the case of resonant Auger decay, this mixing of states also blurs the division of the spectrum into participator and spectator features. Decay spectra resonances assist in the assignment of Rydberg resonances. The decay of the double excitations above the C 1s threshold has also been studied.